Structural and geochronological constraints from the Drina-Ivanjica thrust sheet (Western Serbia): implications for the Cretaceous–Paleogene tectonics of the Internal Dinarides

Abstract

We have investigated successive episodes of ocean-continent and continent-continent convergence in Western Serbia (Drina-Ivanjica thrust sheet). The coupled application of structural and petrological analyses with Illite Crystallinity measurements and K/Ar dating has revealed the timing and structural characteristics of multiple regional deformation phases, and allowed us to revise the origin of the different Triassic units outcropping in the study area. D 1 tectonic burial was characterized by anchizonal metamorphism, dominantly WNW-verging isoclinal folding (F 1), and related axial planar cleavage (S 1) formation in the Paleozoic basement and the stratigraphic cover of the Drina-Ivanjica thrust sheet exposed along the northern rim of this thrust sheet. The timing of D 1 deformation is constrained by K/Ar ages suggesting 135-150 Ma tectonic burial for the Drina-Ivanjica thrust sheet. D 1 deformation and metamorphism is correlated with the closure of the Vardar ocean by top-W to NW ophiolite obduction and the underthrusting of the Adriatic distal passive margin below the oceanic upper plate. Since D 1 structures are lacking in the southern occurrences of Triassic rocks within the study area it is proposed that this Triassic is may not be the original sedimentary cover of the Drina-Ivanjica Paleozoic basement. We propose that this southern Triassic originated from a more external Dinaridic thrust sheet and was transported to its present-day position by a top-NE backthrust presumably during late Early Cretaceous-Paleogene times. Mapscale, NW-SE striking D 2 thrust faults and abundant NW-SE trending F 2 folds observed in all units correspond to the general trend of the Dinaridic orogen and are attributed to the latest Cretaceous-Paleogene collision between Adria and Europe. Regional Latest Cretaceous-Paleogene shortening was followed by strike-slip tectonics (N-S shortening and perpendicular extension) and subsequent Miocene normal faulting in both orogen-parallel and orogen-perpendicular directions driven by slab rollback processes of the Carpathian-Dinaridic realm.

Cretaceous‐Paleogene Tectonics of the Pelagonian Zone: Inferences From Skopelos Island (Greece)

“…Therefore, in our view the Early Cretaceous top‐to‐the‐NW‐W kinematic indicators (now in present‐day coordinates) in the Pelagonian zone are likely to represent the record of underthrusting below the Neotethyan/Vardar ophiolites. This view is also supported by the top‐to‐the‐W structural polarity of obduction‐related deformation in Northeastern‐Albania (Tremblay et al, ), in Western‐Serbia (Porkoláb et al, ), and top‐WNW shear sense indicators in the metamorphic sole and subophiolitic mélange of the Internal Dinarides (Carosi et al, ; Schmid et al, ; Schefer, ).…”

“…Based on stratigraphy and structural position, the Pelagonian zone of the Hellenides can clearly be correlated with the Internal Adria‐derived thrust sheets structurally underlying the obducted ophiolites of the Dinarides (e.g., Schmid et al, ). Early Cretaceous metamorphism in the Internal Dinarides is constrained by K/Ar thermochronology (Milovanović, ; Milovanovic et al, ; Porkoláb et al, ; Tomljenović et al, ), and Early‐to Late Cretaceous metamorphism by 40 Ar/ 39 Ar thermochronology (Schefer, ). Similar to the Pelagonian zone in the Hellenides, WNW‐ESE stretching lineations and top‐WNW sense of shear has been reported from the subophiolitic units marking the tectonic transport direction of the ophiolite thrust sheet(s;Carosi et al, ; Schefer, ; Schmid et al, ).…”

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

“…These similarities and their common structural position below the WVO are in accordance with a common palaeogeographic position on the easternmost tip of the Adriatic continental margin. In western Serbia, the ophiolitic massifs of the WVO (mainly represented by the Zlatibor and the Maljen massifs) have exactly the same geological features and therefore are considered to have had physical continuity, which was disrupted during exhumation of the Drina-Ivanjica Unit (Chiari et al 2011;Porkolab et al 2019). Finally, the more internal Adria-derived unit is represented by the Jadar-Kopaonik Unit, consisting of a Palaeozoic metasedimentary succession overlain by a Middle Permian to Lower-Middle Triassic shallow-water clastic-carbonate sedimentary succession (Robertson et al 2009) passing into Middle Triassic to Jurassic hemipelagic and distal turbiditic carbonates and radiolarites (Schefer et al 2010b).…”

Neoproterozoic-paleozoic evolution of the Drina formation (Drina-Ivanjica entity)

“…It could actually represent two different formations; 2, Questionable occurrence of meta-basic rocks in both formations, missed in the lower section of the column; 3, There should be an unconformity between the Late Carboniferous and the Early Triassic; 4, The interrelationships between the entire set of Paleozoic formations are ongoing work. PORKOLÁB et al (2018).…”

“…The concept of "multiple-oceans" (DIMITRIJEVIĆ & DIMITRIJEVIĆ, 1973;DIMITRIJEVIĆ, 1997) portrays a Middle Triassic-uppermost Jurassic Intradinaridic ocean (DIMITRI-JEVIĆ, 2001) lately also explained via Triassic seapaths between the isolated continental segments of the Dinarides (ARGNANI, 2018). Another concept advocating the "single-ocean" model or "two ophiolites-single ocean" places underthrusting Adriatic distal passive margin (including DIE) below the oceanic upper plate (e.g., PORKOLÁB et al, 2018;SCHMID et al, 2008;TOLJIĆ et al, 2018).…”